/*
 *  Copyright 2013 National Institute of Advanced Industrial Science and Technology
 *  
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *  
 *      http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.sss.server;

import java.util.Iterator;
import java.util.NoSuchElementException;

import org.sss.mapreduce.SideData;
import org.sss.mapreduce.SssException;
import org.sss.mapreduce.Tuple;
import org.sss.mapreduce.datatype.Packable;

public class TupleIterator<K extends Packable, V extends Packable> implements Iterator<Tuple<K, V>> {
  private SideData<K, V> sideData;
  private Iterator<K> keyIt;
  private Iterator<V> valIt;
  private K key;

  public TupleIterator(SideData<K, V> s) {
    try {
      this.sideData = s;
      this.keyIt = s.keys().iterator();
      this.valIt = null;
    }
    catch (SssException e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public Tuple<K, V> next() {
    if (!hasNext()) {
      throw new NoSuchElementException();
    }
    return new Tuple<K, V>(key, valIt.next());
  }

  @Override
  public boolean hasNext() {
    while (valIt == null || !valIt.hasNext()) {
      if (!keyIt.hasNext()) {
        return false;
      }
      key = keyIt.next();

      try {
        valIt = sideData.get(key).iterator();
      }
      catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
    return true;
  }

  @Override
  public void remove() {
    throw new UnsupportedOperationException();
  }
}
